In recent years, in the field of magnetic recording media used in, for example, a hard disk drive (HDD), there has been a marked increase in recording density and the recording density has increased at a high rate of about 1.5 times per year. There are various techniques for supporting the improvement in recording density. For example, one of the key technologies is controlling sliding characteristics between a magnetic head and the magnetic recording medium.
For example, since a CSS (contact start stop) type, which is called a Winchester type, in which a basic operation from the start to the stop of the magnetic head for the magnetic recording medium is performed in the order of contact sliding, floating, and contact sliding is mainly used in the HDD, the contact sliding of the magnetic head on the magnetic recording medium is inevitable.
Therefore, tribology between the magnetic head and the magnetic recording medium is a critical problem and efforts to improve a protective film formed on a magnetic film of the magnetic recording medium have continued. In addition, abrasion resistance and sliding resistance on the surface of the medium are main factors for improving the reliability of the magnetic recording medium.
As the protective film of the magnetic recording medium, films made of various materials have been proposed. However, a carbon film has been mainly used, considering all factors including a film-forming performance and durability. In addition, for example, since the hardness, density, and dynamic friction coefficient of the carbon film are directly reflected in the CSS characteristics or corrosion resistance characteristics of the magnetic recording medium, they are very important.
However, when only the protective film is provided, the durability of the magnetic recording medium deteriorates. Therefore, a lubricant film is formed on the surface of the protective film. The lubricant film has the following main functions: a function of preventing, for example, the protective film of the magnetic recording medium from being directly exposed to the air to improve the corrosion resistance of the magnetic recording medium; a function of preventing a direct contact between a magnetic head slider and the protective film when the magnetic head slider incidentally comes into contact with a data surface of the magnetic recording medium; and a function of significantly reducing the frictional force of the magnetic head slider when the magnetic head slider slides on the magnetic recording medium.
The thickness of the lubricant film formed on the surface of the magnetic recording medium is strictly managed in the range of sub-nanometers. As a method of forming the lubrication film, a so-called dipping method has been widely used which dips a magnetic recording medium in a dip tank filled with a liquid lubricant and draws up the magnetic recording medium from the dip tank, thereby forming a lubricant film with a uniform thickness on the surface of the magnetic recording medium (for example, see PTL 1). In the dipping method, in general, a batch processing method is used in terms of mass production and a plurality of magnetic recording media arranged in a line are dipped into the dip tank and are collectively processed.